Background: Cricoid pressure is dead, right? Many have made this claim including a brilliant argument against its use by John Hinds here. Despite the many eulogies, we continue to hear about cricoid pressure so it makes sense that we dive in to the background prior to addressing the recent JAMA Surgery publication.

Cricoid pressure was first described by Dr. Sellick in the 1960’s though similar techniques were described as far back as the 1770s (Sellick 1961). The Sellick’s maneuver entailed the application of pressure over the cricoid cartilage with the thumb and 1-2 additional fingers.The goal was to compress the cricoid cartilage against the esophagus in order to occlude the esophagus and prevent regurgitation of stomach contents into the upper airway. Initial studies on the maneuver suffered from a bevy of methodological flaws including small n, lack of blinding or randomization and selection bias. Despite this, Sellick’s maneuver was widely adopted and taught to hordes of anesthesia, critical care and emergency residents.

Studies investigating cricoid pressure in the last decade have demonstrated a number of issues with claims that it can prevent passive regurgitation. Check out this free chapter on EMRAP for an in depth discussion. Dynamic MRI studies demonstrate that application of pressure to the cricoid cartilage displaces the esophagus laterally instead of occluding it (Smith 2003, Boet 2012). An ultrasound study demonstrated similar findings: in 60% of patients the esophagus was lateral to the airway and cricoid pressure led to displacement rather than occlusion in all patients. (Tsung 2012).

Additionally, application of cricoid pressure decreases airway patency and increases the chance that your view of the airway will be obscured. (Allman 1995, Palmer 2000, Smith 2002, Oh 2013). Finally, no study to date has demonstrated a reduction in aspiration episodes with the application of cricoid pressure. A large observational study of pregnant patients undergoing C-sections found no difference in aspiration events and that the overall aspiration event rate was low (Fenton 2009). However, up until this point, there has not been a high-quality, randomized controlled trial performed.

Baseline characteristics including level of training of operator were well balanced between groups

Proper training was undertaken to ensure that those supplying cricoid pressure were performing it properly

There were no major protocol violations and only 12 minor violations

Limitations:

This is not a study of ED patients requiring emergency intubation so it is unclear exactly how to apply this to EM practice

The randomization process is not explicitly discussed in the manuscript

It is unclear how many patients were excluded from randomization

Pregnant patients were excluded. This is important because aspiration is a significant cause of maternal death

Pediatric patients were excluded. This evidence cannot be applied to this group

Some patients had nasogastric tubes (13%) before anesthesia, and the decision to remove this was left up to the attending anesthesiologist as well as the decision to administer antacid (12%) before anesthesia, both of which could affect aspiration rates

No standardization of patients with gastric tubes, although this did not change the results of this study

The induction agent wasn’t standardized. It’s unclear if this would have affected the results, though.

Power calculation based on a baseline pulmonary aspiration rate of 2.8% but the rate was considerably lower (just 0.6%) leading to wide confidence intervals around the point estimate

Though the study was blinded, the intubator may have been aware of whether the patient was getting true cricoid pressure or the sham procedure. This may pose a limitation because pulmonary aspiration was gauged partly based on visualization of vomitus by the laryngoscope operator

Discussion:

Technically, this is a negative study – it does not demonstrate non-inferiority of the “sham” maneuver in comparison to cricoid pressure. However, there is an absence of any hint of benefit to cricoid pressure from this data.

The “sham” technique outperformed cricoid pressure in most secondary outcomes including quality of view, improvement of view with removal of criciod/“sham” pressure, intubation time and difficult intubations

Authors Conclusions:

“This large randomized clinical trial performed in patients undergoing anesthesia with RSI failed to demonstrate the noninferiority of the sham procedure in preventing pulmonary aspiration. Further studies are required in pregnant women and outside the operating room.”

Our Conclusions: Although this study failed to demonstrate non-inferiority of sham cricoid pressure to cricoid pressure the data does not show any hint that cricoid pressure is the better approach. In fact, there was a significant difference in terms of difficulty of intubation favoring no application of cricoid pressure and, the difficulty in view was relieved in most cases by removing cricoid pressure.

Potential to Impact Current Practice: Cricoid pressure should not routinely be provided to patients undergoing intubation.

Bottom Line: Occlusion of the esophagus by cricoid pressure appears to be a myth based on MRI and US studies. Previous literature demonstrates that cricoid pressure gives inferior views and no high-quality literature has shown decreased aspiration with application of cricoid pressure.

All of this in conjunction with the numbers seen in this study tells us that pulmonary aspiration is uncommon in the OR setting and isn’t reduced by the application of cricoid pressure. While an ED based study would be nice to have, the current evidence tells us that application of cricoid pressure is unlikely to benefit our patients but is likely to make our intubation more difficult.